Turbota wrote one important sentence.
Once all cams are removed, DO NOT rotate the engine. This will make it much easier to install the new cams in there proper position.

Here I made a mistake. My cams was removed and I had move the bike in my garage. Of course, I forgot 5th gear and my engine rotated

Can you please advise me how I can install the cams properly now?

Thanks a lot for every advice

Mark

It doesn't make it much more difficult. Just rotate the engine until the mark on the pinion gear is pointing to the centre of the bush for the #2 cam (edit: as in Rico's photo above - he beat me to it!), then install the #2 cam to check the mark on it aligns with the mark on the pinion gear (remove the cam and rotate the engine slightly if necessary to align).

Now remove the #2 cam.

Fit the #1 and #3 cams and align the marks on them with the centre of the #2 cam bush. Hold them in place while you reinstall the #2 cam. Check that all marks on cams 1-3 and the pinion gear align. Slide the #2 cam out slightly if necessary to adjust the alignment of cams 1 and 3.